Abstract:

Chronic idiopathic urticaria is a common skin disorder characterized by recurrent appearance of wheals and/or
angioedema for more than 6 weeks without an identifiable cause. Consensus guidelines suggest use of leukotriene
receptor antagonists (montelukast or zafirlukast) in patients whose urticaria is resistant to antihistamines. Our objectives
were (1) document the efficacy of montelukast in our patients, and (2) evaluate whether any clinical features or available
laboratory investigations were associated with a response to montelukast.

Patients who received montelukast between the years 2008-2011 (4-year period) were retrospectively identified from
clinic letters. Clinical features and laboratory investigations were collected and analyzed. The primary end point was
adequate control of disease without the need for systemic steroid therapy.

25 patients (10 males and 15 females; median age, 33 years; age range, 13-66 years) with an average duration of urticaria
at 3.8 years received montelukast 10mg daily. 12 patients (48%) were better on montelukast with combined anti-H1 and
anti-H2 therapy, with no statistical significance between median age and duration of urticaria between males and females.
In 11 patients, montelukast had no effect and in 2 patients the urticaria worsened after montelukast was started. 15 patients
had peripheral blood basopenia of which 5 patients responded to montelukast. Two patients had positive antinuclear
antibody, 3 thyroid peroxidase antibodies and 4 with positive basophil histamine release. All 20 patients who had
complement C3 and C4 levels done were within normal limits. Four of 6 patients (67%) with positive specific IgE
responded to montelukast and combined anti-H1/H2 therapy.

Almost half of our patients with chronic urticaria responded to montelukast and combined anti-H1 and anti-H2 therapy.
We were unable to identify any clinical features or laboratory markers that were associated with a response to
montelukast. Further studies are required to understand the failure of response of leukotriene inhibition in urticaria.

Abstract:Chronic idiopathic urticaria is a common skin disorder characterized by recurrent appearance of wheals and/or
angioedema for more than 6 weeks without an identifiable cause. Consensus guidelines suggest use of leukotriene
receptor antagonists (montelukast or zafirlukast) in patients whose urticaria is resistant to antihistamines. Our objectives
were (1) document the efficacy of montelukast in our patients, and (2) evaluate whether any clinical features or available
laboratory investigations were associated with a response to montelukast.

Patients who received montelukast between the years 2008-2011 (4-year period) were retrospectively identified from
clinic letters. Clinical features and laboratory investigations were collected and analyzed. The primary end point was
adequate control of disease without the need for systemic steroid therapy.

25 patients (10 males and 15 females; median age, 33 years; age range, 13-66 years) with an average duration of urticaria
at 3.8 years received montelukast 10mg daily. 12 patients (48%) were better on montelukast with combined anti-H1 and
anti-H2 therapy, with no statistical significance between median age and duration of urticaria between males and females.
In 11 patients, montelukast had no effect and in 2 patients the urticaria worsened after montelukast was started. 15 patients
had peripheral blood basopenia of which 5 patients responded to montelukast. Two patients had positive antinuclear
antibody, 3 thyroid peroxidase antibodies and 4 with positive basophil histamine release. All 20 patients who had
complement C3 and C4 levels done were within normal limits. Four of 6 patients (67%) with positive specific IgE
responded to montelukast and combined anti-H1/H2 therapy.

Almost half of our patients with chronic urticaria responded to montelukast and combined anti-H1 and anti-H2 therapy.
We were unable to identify any clinical features or laboratory markers that were associated with a response to
montelukast. Further studies are required to understand the failure of response of leukotriene inhibition in urticaria.